Rusted Fuel Tanks

[K-Mo]

I have severely rusted fuel tanks on Briggs & Stratton engines on equipment that sat outside for a couple of years. The kind with the carburetor mounted on the fuel tank.
To replace a tank, I went to my salvage pile and pulled out a couple of engines that had been in the pile for several years. Found the tanks to be good.
Began to wonder why. Would ethanol draw moisture causing the tanks to rust?
The tanks don't have a drain to remove the fuel when the equipment is not in use.

 

[Stephen Newell]

More than likely the good tanks the caps sealed out the water better. All ethanol will do is allow moisture to mix with the gas. It otherwise gas would float on top of the water. Before ethanol gas, when condensation got into the gas tank you could see the water roll around the bottom of the tank like a bubble.

 

[T.R.K.]

You get enough water in ethanol blend and both the water and the ethanol will go to the bottom of the tank too. That is one way to determine what percent ethanol you have in a particular sample.

And since ethanol is a fermented product, it really likes to mix with water much better than the gas it is mixed in.

 

[K-Mo]

I sent an email to B/S. This is what they said--

Here is information on ethanol issues in fuel that is the most likely cause of rusting in the fuel tank.

Ethanol Issues in Fuel
Ethanol can soften hoses and gaskets, dissolve your carburetor float and other plastic parts, and corrode metal.

Ethanol, created by blending gasoline and ethyl alcohol, is added to gasoline to make an environmentally friendly product and to help conserve fuel resources. Ethyl alcohol is grain alcohol that has been used in vehicles since the 1970s. In recent years, ethanol has been shown to cause problems in small engines, such as those found in ATVs, recreational watercrafts, boats and lawnmowers, and consumer warnings have been issued by some manufacturers.

Phase Separation - Consumer Affairs reports that ethanol fuel is particularly harmful to some vehicles, especially boats, because of a process known as phase separation. Phase separation occurs because ethanol attracts and binds with water. When ethanol absorbs too much water, the ethanol and water separate from the gasoline, leaving behind a layer of water that can seriously damage an engine when the vehicle attempts to burn fuel. Lawnmower manufacturer Briggs and Stratton does not recommend leaving ethanol fuel in engines for more than 30 days without adding fuel stabilizer to the engine.

Potential Engine Corrosion - The alcohol content in ethanol could cause engine corrosion. Ethanol gasoline has been known to break down engine seals, dissolve fiberglass gas tanks in boats and destroy plastics. Over time, ethanol's corrosive properties can lead to engine failure, especially if corrosion winds up in the engine causing clogs and fuel blockage. Due to emission controls the carburetors are now manufactured with smaller passages than in the past.

Storage
Storing for the winter ? run the tank dry or store with fuel? That's an important question. Visit any repair shop and you'll see the problems that E10 gasoline?which is actually 10 percent ethanol?can cause in small air-cooled engines. The alcohol in the fuel dissolves plastic and rubber parts in the fuel system. It also attracts moisture. which leads to corrosion of metal parts. And even if the engine escapes damage, it experiences a loss of performance from chemically degraded fuel, because ethanol-based gasoline can spoil rapidly, often separating into layers of alcohol and fuel

I hope this is helpful in answering your question.

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